Xerox 242 second side of paper with different colours

Hi,

I have problem with different colors on second side of paper.

I print from bypass tray manually on both sides coated 280 gsm paper (paper is two side coated). So basically I print the same file all sheets the same with one color mix and second side of paper with the same file but colors are differently mixed... I can see its too much cyan, maybe black etc. I thought maybe it has something with humidity or electrostatics, so I leave the one printed side papers to rest for the night. But its not the case as it prints second side differently even then after. Its the same if I print only one sheet, reverse it backside and print.

Any thoughts i should check?